During embryonic development, EphB4 and EphrinB2 are both critically required for maturation of newly forming blood vessels. EphrinB2 and is critically required for activation of VEGFR2/3. EphrinB2 is up-regulated in tumor vasculature and loss of EphrinB2 led to arrested tumor angiogenesis and inhibited tumor growth. On the other hand, EphB4 is highly induced in many epithelial cancers and serves as a tumor survival factor. EphB4 expressed on tumor cells also interacts with EphrinB2 on tumor vessels and promotes both the tumor cell survival and the tumor angiogenesis. We have developed an EphB4-EphrinB2 inhibitor - the extracellular fragment of EphB4 fused with human serum albumin (sEphB4-HSA). In SBIR phase I project, we have shown that sEphB4-HSA inhibits tumor growth and causes tumor regression in many xenograft and spontaneous tumor models, and combination with chemotherapy agents has additive/synergistic effect. Particularly sEphB4-HSA is highly effective in regressing Kras mutant driven tumors in xenograft and genetic tumor models. We have produced GMP quality sEphB4-HSA and performed GLP pharmacokinetics (PK) and toxicology studies in mice and monkeys. The IND application has been approved and sEphB4-HSA now is in human phase I clinical trial. First three dose levels have been accrued and no dose limiting toxicity has been observed. None of the patients have experienced grade three or grade four toxicity. There are also signs of clinical benefit. One patient at the lowest dose (2.5mg/kg) has had stable disease at 4 months since the initiation of the treatment. Three patients including a kras lung adenocarcinoma at the second dose level (5mg/kg) have stayed on therapy for 3-4 months and all have had stable diseases and two have shown signs of tumor regression. Therefore, we will manufacture large quantity (1.7 kg) of sEphB4-HSA for the coming human Phase II clinical trials in Kras mutant lung and pancreatic cancers. To determine the treatment regimens, we will conduct efficacy studies in genetic Kras mutant mouse models (with or without concurrent p53 mutation). We will test sEphB4-HSA as a single agent and also combined with chemotherapy agents. Finally we will collect blood from patients at various time points and apply novel technology to isolate circulating tumor cells and analyze the expression of sEphB4-HSA targets. We will also analyze the circulating levels of VEGF and soluble VEGFR2, two known biomarkers of anti-angiogenesis therapies. These results will guide us to identify the pharmacodynamic biomarker of sEphB4-HSA, which will be very useful in the evaluation of patient responses in the clinic.